1. Field of the Invention
The disclosures herein relate to a display apparatus provided with an optical pointing device.
2. Description of the Related Art
Pointing devices that have been used include the one that detects an electrical change caused by electrostatic or electromagnetic induction when a pen comes in contact with a sensor surface or comes close to the sensor surface. Patent Document 1 (see the list of documents attached at the end of the description of embodiments) discloses another type of device that is an ultrasonic touch panel pointing device. This device detects the position of an object based on attenuation of surface acoustic waves caused by the object coming in contact with a panel on which the surface acoustic waves are propagating.
Further, Patent Document 2 and Patent Document 3 filed by the inventor of the present application disclose an optical touch panel display in which a shadow of a pen or finger is optically detected to calculate the coordinates of the contact point based on triangulation.
Further, Patent Document 4 also filed by the inventor of the present application discloses a mechanism that can change an elevation angle and depression angle of a display. Patent Document 5 discloses a rotation mechanism allowing rotation in a display plane.
The optical touch panel display disclosed in Patent Documents 2 and 3 perform calibration at the time of startup or at constant intervals. To be specific, an optical intensity distribution on an image sensor provided in the optical touch panel is stored in memory under the condition in which no pen or finger (hereinafter collectively referred to as a stylus) is not placed on the display surface. When a stylus is placed on the display surface (i.e., inserted into a detection plane), a resulting optical intensity distribution on the image sensor is compared with the optical intensity distribution stored in the memory to calculate a difference, thereby detecting the position at which the stylus is placed (or inserted). This is aimed at removing the effect of background components in an optical intensity distribution on the image sensor when such an effect is created by illumination light or the like that may vary depending on the place or time at which the optical touch panel display is used.
As disclosed in Patent Documents 4 and 5, the position of a display may be changed. When such a positional change occurs, and especially when the display surface is rotated as disclosed in Patent Document 5, there is a significant change in the relative positional relationship between the touch sensor provided in the touch panel attached to the display and the ceiling light or outside light coming through windows. Because of this, there is a need to perform calibration. Such calibration may need to be performed immediately upon a change in display position.
In typical display products provided with an optical touch panel, however, calibration is performed at the startup of the display or at constant intervals. Alternatively, users may need to be conscious and explicitly initiate calibration (e.g., through selection on the menu screen).
Accordingly, there may be a need to provide a display apparatus with an optical touch panel that can accurately detect coordinates by removing the effect of ambient light through an automatic calibration function that is executed when a positional change of the display apparatus occurs, such as a change in its location through movement in a vertical or horizontal direction or a change in its position regarding an elevation angle, a depression angle, an azimuth angle, and/or in-plane rotation.